Electronic seam welding for high speed welding



QLML .May '7, 1940. J. w. DAWSON ELECTRONIC SEAM WELDING FOR HIGH SPEEDWELDING Original Filed May 7, 1938 Fi i WITNESSES:

INVENTOR John 1411 Dawson.

ATTORNE Patented May 7, 1940 UNITED STATES PATENT OFFICE ELECTRONIC SEAMWELDING FOR HIGH SPEED WELDING Pennsylvania Original application May I,1938, Serial No.

Divided and this application Februmy 4, 1939, Serial No. 254,811

3 Claims.

My lnventionrelates to a welding system and particularly to anelectronic seam welding control for high speed welding.

An object of the invention is to utilize multi-- 5 phase current forenergizing the electrodes of a welding system.

Another object of the invention is to multiply the frequency of analternatlng'current source.

Another object of the invention is to use a higher frequency ofalternating current on the welding electrodes than that of the usualcommercial current.

Other objects and advantages of the invention will be apparent from thefollowing description and drawing, in which Figure l .is a diagrammaticcircuit illustrating a preferred application of the invention; and

Fig. 2 is a graph illustrating the multi-phase energizing voltage andthe higher frequency of the welding current.

This application is a division of my application Serial No. 206,638,filed May 7, 1938, and assigned to the Westinghouse Electric &Manufacturing Company of East Pittsburgh, Pa.

It has been found that production speed in applications of scam weldingutilizing continuous single phase 60-cycle current was limited becauseof leaks resulting from welds too far apart.

In the canning industry, for example, the pres- 30 ent production speedis 300 to 350, five inch cans per minute which speed is too fast forpresent types of welders. I have accordingly designed my invention toutilize multi-phase current instead of this continuous single phaseBil-cycle current and also to provide a higher frequency of cycles asapplied to the welding electrodes. In Fig. 1, I have disclosed thecurrent lines of a multi-phase system comprising the lines In, I I and12. These lines may be of usual 60-cycle commercial cur- 40 rent.Connected to these lines is a three-phase transformer I3 having aprimary I4 and a secondary I5 of preferably Y-shape having terminals A,B and C and a common terminal 9. The welding electrodes I6 and I1,preferably in the form of rollers to provide seam welding on the work orload 18, are connected through a welding transformer I9 to the secondaryI5 of the multiphase transformer.

The particular welding load illustrated is the cylindrical side I8 of atin can having its lateral seam I8 welded under the roller Hi. The tincan is held in a suitable mandrel and the current may return throughanother roller H or by a connection to the mandrel. The top and bottomof the can may also be welded. One end 23 of the primary 20 of thewelding transformer I9 is preferably connected through 22 to the commonpoint of the three-phase transformer secondary I 5. Intermediate theother end 2 I of the primary of the welding transformer and the variousterminals A, B and C of the multi-phase transformer I are preferably aplurality of electric valves I, 2, 3, 4, 5 and 5. These valves may takevarious forms, but I prefer to utilize the construction of an arcdischarge device under makealive control, as described in the patent toSlepian et al. No. 2,069,283, issued February 2, 1937. The terminal A oftransformer secondary I5 is connected by 24 to the anode 25 of electricvalve I and to the cathode 25 of electric valve 2. The cathode 21 ofelectric valve I and the anode 28 are connected by 29 to the terminal iiof the primary 20 of the welding transformer I9. The terminal B isconnected by 30 in a similar manner to the anode ill of electric valve 3and cathode 32 of electric valve 4 and the cathode 33 of electric valve3 and the anode 34 of electric valve 4 are connected to 29, which, inturn, extends to the terminal 2| of the primary 29 of the weldingtransformer I9. In a similar manner, the terminal C is connected by 35through the anode 3B of valve 5 and cathode 31 of the valve Ii acrossthe discharge space to the cathode 38 of valve 5 and anode 39 of valve 6to the connection 29 and the welding transformer primary 20. In order toenergize the respective make-alives 40, 4!, 42, 43, 44 and 45 of theelectric valves I through 6, I provide discharge devices 46, 4?, 48, 49,50 and 5I, having their anodes connected to the anodes of the valves andtheir cathode connected to the make-alives.

Each of these discharge devices has the discharge therethrough undercontrol of the respective grids 52, 53, 54, 55, 56, and 51. The gridsand cathodes of these discharge devices are preferably connected to aplurality of coils 58, 59, 60, BI, 52 and 63 through a Y-connectedsecondary to a three-phase primary 64 preferably energized through asuitable phase shift de-- vice 65 from the multi-phase lines I0, I I,and I2,

The coils 58 and 59 form one leg of the Y secondary 66, and theconnections to the coil 59 and tube 41 are reversed to that of theconnections between coil 58 and the discharge device 46. Similarly, thecoils 60 and BI form another leg of the secondary B6 and 52, and 63likewise forms the third leg.

The phase shift device 55 is utilized to control the portion of thewelding current desired in each phase. The secondary 55 energizes thevarions grids 52 to I1 to permit the respective discharge devices 46through 5| to energize. in turn, the make-alives 40 through 45. Theoperation of the device will be more apparent by including reference toFig. 2. This figure discloses the three-phase voltage as applied to theterminals A. B and C of the secondary IS. The circuit is connected andapplied at the point III on the point A of Fig. 2. This means a positivevoltage at the terminal A and this voltage will fire electric valve Iand the current will pass through I to the cathode 21 and connection 29,primary 20 and back to the common point 0, thus energizing the secondary68 of the welding transformer and also the welding electrodes [6 and [1.This welding current begins at point H on the zero line of Fig. 2 andhas the positive half cycle 12 illustrated in Fig. 2. The length of thiscycle is short because the energizing coil 58 is only part of a leg onthe secondary 6G. The welding current through this particular valve Istops at the point I3 and there is preferably a short interval 14between the termination of this half cycle and the next half cycle whichcan be arranged by adjustment of the phase shift device 65. The halfcycle 12 of the welding current is passed from the terminal A throughthe primary 20 and back to the common point 0 through the secondary IS.The next half cycle will be in the opposite direction and at this timethe wave of current will be negative in phase 0 as indicated on thedrawing. The reverse phase will accordingly pass from 0 through 20through the electric valve and will return it to phase C. This happensto be the electric valve 8 and has its anode connected to the terminal23 of the primary 20 and its cathode to the terminal C of secondary I5.The electric valve 6 will be energized at 15 and continue its half waveof welding current 16 until it decreases at H to zero. For the next halfcycle of welding current, a positive half cycle of welding current fromone of the legs of the transformer is necessary and this means a passageof current from B through the electric valve 3 to the primary 20 andback to the common point II. This is indicated on the curves of Fig. 2by the half cycle 18 extending between the points 19 and ll. The nexthalf cycle 8| of welding current will be negative and will pass from thecommon point 0 through primary 20 of the welding transformer and theelectric valve 2 to the terminal A. In a similar manner, the nextpositive halt cycle of current will be from 0 through the electric valveI to the primary 20 and back to the common point I. The last half cyclewill be from the common point I through the primary 20 and electricvalve 4 to the phase B.

It will be noted that the energizing current applied to the weldingelectrodes l8 and I1 is that of multi-phase current in contrast to thecontinuous current heretofore utilized. Furthermore, the number ofcycles applied to the welding load has been multiplied by three with theresult that 180 cycle current is utilized in the load in place of the-cycle current supplied by the commercial lines. The number of cyclescould be still further multiplied if desired by increasing the number ofelectric valves and auxiliary control circuits.

Many modifications may be made in the preferred embodiment withoutdeparting from the spirit of the invention. Accordingly, I desire onlysuch limitations to be placed upon the following claims as isnecessitated by the prior art.

I claim as my invention:

1. In combination with a single pair of welding electrodes for makingmoving contact with an article to be welded, a source of polyphasealternating current, and at least one unilaterallyconductedcurrent-carrying device connected between each phase terminal of saidpolyphase source and the circuit of said electrodes.

2. In combination with a single pair of welding electrodes for makingmoving contact with an article to be welded, a source of polyphasealternating current, the fundamental frequency of said source being solow relative to the speed of movement of said article relative to saidelectrodes that if single-phase current of said fundamental frequencywere applied directly to said electrodes discontinuities would existbetween successive welded areas on said article, and at least oneunilaterally-conducting current-carrying device connected between eachphase terminal of said polyphase source and the circuit of saidelectrodes.

3. In combination with a single pair of welding electrodes, a source ofpolyphase alternating current, and a pair of back-to-back connectedunilaterally-conducting current-carrying devices connected between eachphase terminal or said polyphase source and the circuit of saidelectrode.

JOHN W. DAWSON.

